1. Field of the Invention
The present invention relates to a process for manufacturing structures on a substrate. More specifically, the present invention relates to creating optical components within an integrated circuit through a process that uses chemically-selective endpoint detection.
2. Related Art
The dramatic advances in computer system performance during the past 20 years can largely be attributed to improvements in the processes that are used to fabricate integrated circuits. By making use of the latest fabrication processes, integrated circuit designers can presently integrate computing systems comprised of hundreds of millions of transistors onto a single semiconductor die which is a fraction of the size of a human fingernail.
Integrated circuit fabrication technology is also being used to fabricate optical devices such as lasers within integrated circuit devices, and which have dimensions measured in fractions of microns.
A typical fabrication process builds structures through successive cycles of layer deposition and subtractive processing, such as etching. As the dimensions of individual circuit elements continue to decrease, it is becoming necessary to more tightly control the etching operation. For example, in a typical etching process, etching is performed for an amount of time that is estimated by taking into account the time to etch through a layer to reach an underlying layer, and the time to overetch into the underlying layer. However, this process can only be controlled to +/xe2x88x92100 Angstroms, which can be a problem when fine control of dimensions is required.
Furthermore, conventional etching processes that indiscriminately etch all exposed surfaces are not well suited to manufacture some structures that require tighter control over subtractive processing operations. As circuit structures become smaller, there is less tolerance available to account for uncertainties in the manufacturing process.
Additionally, connecting optical devices within an integrated circuit typically requires aligning optical fibers with an optical device such as a laser, or converting the optical signals to electrical signals at the source and converting the electrical signals back to optical signals at the destination. Aligning optical fibers with an optical device is difficult and time consuming because of the small dimensions involved, while converting the form of the signals can lead to signal degradation.
What is needed is a method of fabricating and connecting optical components that does not have the difficulties listed above.
One embodiment of the present invention provides a system to facilitate using selective etching to form optical components on a circuit device. The system operates by receiving a substrate composed of a first material including a buffer layer composed of a second material. The system forms a sacrificial layer composed of a third material on the buffer layer. Next, the system forms an optical fiber core composed of a fourth material on the sacrificial layer. After the optical fiber core has been formed, the system performs an etching operation using a selective etchant to remove the sacrificial layer. The system also applies a cladding layer to the optical fiber core.
In one embodiment of the present invention, the system adds a filler to fill the cavity left by removing the sacrificial layer and planarizes the circuit device using chemo-mechanical polishing to create a planarized surface.
In one embodiment of the present invention, the substrate is Si and the buffer layer is SiGe or SiGeC. Using SiGeC for the buffer layer allows growth of a thicker buffer layer than when using SiGe. In this embodiment, the sacrificial layer is Si, the optical fiber core is SiO2:GeO2, the selective etchant used to remove the sacrificial layer is KOH or tetramethylammonium hydroxide (TMAH), and the cladding layer on the optical fiber core is SiO2. It is appreciated that other materials and etchants may be used.
In one embodiment of the present invention, the buffer layer is SiGeC, wherein carbon is greater than or equal to one atomic percent.
In one embodiment of the present invention, the buffer layer is SiGeC, wherein carbon is less than or equal to one atomic percent.
In one embodiment of the present invention, the filler is SiO2.
In one embodiment of the present invention, the buffer layer is an epitaxial layer.
In one embodiment of the present invention, the sacrificial layer is an epitaxial layer.
In one embodiment of the present invention, the optical fiber core is an epitaxial layer.
In one embodiment of the present invention, the system splits the optical fiber core into multiple optical fiber cores to form an optical multiplexer.
In one embodiment of the present invention, the system combines multiple optical fiber cores into a single optical fiber core to form an optical demultiplexer.
One embodiment of the present invention provides a system to facilitate integrating active or passive components on a circuit device that includes an optical fiber core that was epitaxially grown. During operation, the system receives this circuit device, and etches a cavity into the circuit device, wherein the cavity passes through the optical fiber core. The system also creates an active device within the cavity that is aligned with the optical fiber core.
In one embodiment of the present invention, etching the cavity includes etching into a buffer layer below the optical fiber core.
In one embodiment of the present invention, etching the cavity includes etching into a substrate layer below the optical fiber core.
In one embodiment of the present invention, the substrate layer includes a doped semiconductor region that can form part of the active device.
In one embodiment of the present invention, the system applies a metallization layer to the active device to form conduction paths for the active device.
In one embodiment of the present invention, the metallization layer forms a mirror metallization.